Remote Assistance problem in XP sp2 " program could not start "

[Guest]

iam having Xp Sp2 machine,from which i was not able start remote assistance
invitation . error "program could not start ,try again".i can able to
connect Xp sp1 machine using Remote assistance from SP2 machine but not to
SP2 machine.

 

[Guest]

Start, Control Panel, Windows Firewall.
Exceptions Tab
Make sure there's a check in Remote Assistance

Good Luck